1. Field of the Invention
The subject invention relates to a vehicle foot pedal assembly having an electronic control with a hysteresis generating structure incorporated therein.
2. Description of the Prior Art
Accelerator and brake foot pedal assemblies are used to mechanically control a vehicle engine and brakes, respectively. The foot pedal assemblies usually include a pedal arm mounted to a vehicle body with a series of links and levers connecting the pedal arm to an associated device, such as a carburetor, fuel injector, controller, brake drum, brake housing, or the like. These linkages must be designed to withstand and accommodate engine movements relative to the vehicle frame, as well as provide accurate control despite such movements. In addition, packaging space must be provided for the linkages to function properly. The space available for routing the mechanical control links, rods, and cables is limited.
An improvement in the automotive industry relating to foot pedal assemblies is the use of drive-by-wire systems. Drive-by-wire systems allow the control of the vehicle engine or brakes without the need for a direct mechanical connection between the pedal arms and the engine or brakes. These systems utilize electrical or electronic means rather that mechanical links.
In the drive-by-wire systems, it is important that the pedal arm provide the customary feel and performance of a mechanical linkage. The foot pedal assemblies should function responsively to driver input and should provide non-fatiguing resistance. Drivers are accustomed to certain applying and releasing pressures on a pedal arm and have become accustomed to the resistance force of the pedal arm as well as the rate of withdrawal as the applied pressure is relaxed.
Typically, the pedal arm pressure required when advancing an accelerator pedal, for example, is greater than that required to maintain a fixed position. This difference is often referred to as a hysteresis effect. This effect is important in maintaining the pedal arm in position while driving at a relatively constant speed or for continuous braking. The pressure which must be applied in accelerating, for example, is easily borne but if the back pressure of an accelerator spring produced the same effect during the time it was required to retain or maintain speed, it would soon become uncomfortable for the driver to maintain a relatively constant speed. The hysteresis effect provides relief and lessons the load required to maintain a setting of the pedal arm. Yet there is still force to cause reverse pedal action when the applied pressure is removed.
The hysteresis effect is also important for eliminating undesirable accelerations, decelerations, and uneven brakeages as the vehicle is driven over rough terrain, such as bumpy roads. When the vehicle is driven over a bumpy road, the driver""s foot follows the terrain causing the vehicle to accelerate, decelerate, or brake unevenly, which is undesirable. Thus, hysteresis is needed to provide stability to the vehicle over rough terrain.
Drive-by-wire systems for vehicle engines with hysteresis generating mechanisms are known. One such device is shown in U.S. Pat. No. 5,408,899. Often these hysteresis generating mechanisms are complex, include a significant number of parts, and are difficult to assemble.
An improved drive-by-wire system with a hysteresis generating mechanism is disclosed in U.S. Pat. No. 6,158,299 and is assigned to the assignee of the subject invention. The invention of the ""299 patent provides a pedal assembly having an electronic control with a hysteresis generating mechanism which is simplified, requires fewer components, and is easier to maintain and assemble than the prior systems.
The subject invention is a further improvement of the design disclosed in the ""299 patent such that even a greater hysteresis effect can be realized.
SUMMARY OF THE INVENTION AND ADVANTAGES
A pedal assembly comprising a housing having at least one inner surface. A pedal arm is pivotally connected to the housing for movement between a rest position and an operative position. The pedal arm has a first end and a second end. A resilient member is partially received within the housing. The resilient member has a first distal end and a second distal end with the first distal end seated against the housing and the second distal end engaging the second end of the pedal arm to provide resistance during the movement of the pedal arm. A cap is at least partially disposed over the second end of the pedal arm. The pedal assembly is characterized by the cap including a first portion and a second portion with the second distal end of the resilient member engaging at least one of the first and second portions of the cap. The second portion is movable relative to the first portion when the pedal arm moves between the rest and operative positions such that at least one of the first and second portions engages the inner surface of the housing to provide increased resistance during the movement of the pedal arm.
The present invention, therefore, creates a greater hysteresis effect such that the customary feel during the application of force on the pedal arm as well as the familiar return movement of the pedal arm is realized with a drive-by-wire system.